CN108602394B

CN108602394B - Pneumatic tire

Info

Publication number: CN108602394B
Application number: CN201780011112.9A
Authority: CN
Inventors: 甲田启; 新泽达朗; 植村卓范
Original assignee: Yokohama Rubber Co Ltd
Current assignee: Yokohama Rubber Co Ltd
Priority date: 2016-02-15
Filing date: 2017-02-14
Publication date: 2021-03-09
Anticipated expiration: 2037-02-14
Also published as: WO2017141912A1; CN108602394A; DE112017000829T5; JP6358395B2; US11752805B2; JPWO2017141912A1; US20210213786A1

Abstract

The invention provides a pneumatic tire which can improve the driving stability performance on a dry road surface and improve the driving stability performance on a wet road surface by designing the chamfer shape of a sipe. A pneumatic tire having a plurality of main grooves (9) extending in the circumferential direction of the tire in a tread portion (1), and a sipe (11) extending in the tire width direction in a rib (10) defined by the main grooves (9), wherein the sipe (11) has a step-in side edge (11A) and a kick-out side edge (11B), a chamfer portion (12) shorter than the sipe length (L) of the sipe (11) is formed in each of the edges (11A,11B), a non-chamfered region (13) having no other chamfer portion is present at a position of the sipe (11) opposed to each chamfer portion (12), the maximum depth x (mm) of the sipe (11) and the maximum depth y (mm) of the chamfer portion (12) satisfy the relationship of equation (1), and in a range from an end portion of the chamfer portion (12) located inside in the tire radial direction to the groove bottom of the sipe (11), the sipe width (W) of the sipe (11) is constant.

Description

Pneumatic tire

Technical Field

The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire capable of achieving both improvement of driving stability performance on a dry road surface and improvement of driving stability performance on a wet road surface by designing a chamfered shape of a sipe.

Background

Conventionally, in a tread pattern of a pneumatic tire, a plurality of sipes are formed in a rib defined by a plurality of main grooves. The provision of such sipes ensures drainage and exhibits driving stability on wet road surfaces. However, there are disadvantages as follows: when a large number of sipes are disposed in the tread portion in order to improve the steering stability performance on a wet road surface, the rigidity of the ribs is lowered, and thus the steering stability performance and uneven wear resistance performance on a dry road surface are lowered.

Further, various pneumatic tires in which sipes are formed in the tread pattern and chamfered have been proposed (for example, see patent document 1). When the sipe is formed and the chamfer is performed, an edge effect may be lost due to the shape of the chamfer, and the improvement of the driving stability performance on a dry road surface or the driving stability performance on a wet road surface may be insufficient due to the size of the chamfer.

Documents of the prior art

Patent document

Patent document 1: japanese Kokai publication Hei-2013-537134

Disclosure of Invention

Problems to be solved by the invention

The purpose of the present invention is to provide a pneumatic tire capable of achieving both improvement in driving stability performance on dry road surfaces and improvement in driving stability performance on wet road surfaces by designing the chamfered shape of sipes.

Technical scheme

The pneumatic tire of the present invention for achieving the above object has a plurality of main grooves extending in the circumferential direction of the tire in a tread portion, and sipes extending in the tire width direction are provided in ribs defined by the main grooves, characterized in that the sipe has an edge on a step-in side and an edge on a kick-out side, and chamfered portions shorter than the sipe length of the sipe are formed on the edge on the step-in side and the edge on the kick-out side, non-chamfered regions having no other chamfered portion exist at positions of the sipe facing the respective chamfered portions, the maximum depth x (mm) of the sipe and the maximum depth y (mm) of the chamfered portion satisfy the following equation (1), the sipe width of the sipe is fixed in a range from an end portion of the chamfered portion located on the inner side in the tire radial direction to the groove bottom of the sipe.

x×0.1≤y≤x×0.3+1.0 (1)

Advantageous effects

In the pneumatic tire in which the ribs defined by the main grooves include the sipes extending in the tire width direction, the edges on the step-in side and the kick-out side of the sipes are provided with chamfered portions shorter than the sipe length of the sipe, respectively, and on the other hand, non-chamfered regions having no other chamfered portion are present at positions of the sipe facing each chamfered portion, whereby the water drainage effect can be improved by the chamfered portions and the water film can be effectively removed by the edge effect in the non-chamfered regions. Therefore, the driving stability on a wet road surface can be greatly improved. Further, since the chamfered portion and the non-chamfered portion are mixed in the rim on the step-in side and the rim on the kick-out side, the above-described effect of improving the moisture performance can be obtained to the maximum extent at the time of braking and driving. Further, since the chamfered area can be minimized as compared with a conventional chamfered sipe, the steering stability performance on a dry road surface can be improved. As a result, the improvement of the driving stability performance on a dry road surface and the improvement of the driving stability performance on a wet road surface can be achieved at the same time.

In the present invention, it is preferable that both end portions of the sipe are opened at the main groove. This improves the balance of the rigidity of the rib, and as a result, improves uneven wear resistance.

In the present invention, the sipe preferably has a raised portion. This makes it possible to achieve both improvement of the driving stability performance on dry road surfaces and improvement of the driving stability performance on wet road surfaces. The elevation of the sipe may be performed at the ends of the sipe, or may be performed beyond the ends.

In the present invention, it is preferable that the height of the raised portion disposed other than the end portion of the sipe is 0.2 to 0.5 times the maximum depth x of the sipe. By setting the height of the raised portion disposed at a position other than the end portion of the sipe to an appropriate height in this manner, the rigidity of the block can be improved, and the drainage effect can be maintained, so that the steering stability performance on a wet road surface can be improved. More preferably 0.3 to 0.4 times.

In the present invention, it is preferable that the height of the raised portion disposed at the end of the sipe is 0.6 to 0.9 times the maximum depth x of the sipe. By setting the height of the raised portion disposed at the end of the sipe to an appropriate height in this manner, the rigidity of the block can be improved, and the steering stability performance on a dry road surface can be improved. More preferably 0.7 to 0.8 times.

In the present invention, it is preferable that the sipe is inclined with respect to the tire circumferential direction. By inclining the sipe in this manner, the pattern rigidity can be improved, and the steering stability performance on a dry road surface can be further improved.

In the present invention, it is preferable that the inclination angle of the sipe with respect to the acute-angle side in the tire circumferential direction is 40 ° to 80 °. By setting the inclination angle of the sipe with respect to the acute angle side in the tire circumferential direction in this way, the steering stability performance on a dry road surface can be more effectively improved. More preferably 50 to 70.

In the present invention, the chamfer portion is preferably disposed on the acute angle side of the sipe. This can further improve uneven wear resistance. Alternatively, the chamfer portion is preferably disposed on the obtuse side of the sipe. This enhances the edge effect, and can further improve the driving stability on a wet road surface.

In the present invention, it is preferable that at least a part of the sipe is curved or flexed in a plan view. By forming at least a part of the sipe in this manner, the total amount of edges of each sipe is increased, and the driving stability performance on a wet road surface can be improved. The overall sipe may be arcuate.

In the present invention, it is preferable that the chamfered portion is open to the main groove. This can further improve the driving stability on a wet road surface. Alternatively, it is preferred that the chamfer terminates within the rib. This can further improve the driving stability on a dry road surface.

In the present invention, it is preferable that the overlapping length of the chamfer formed at the edge of the step-in side of the sipe and the chamfer formed at the edge of the kick-out side of the sipe is-30% to 30% of the sipe length. By appropriately setting the overlap length of the chamfered portion with respect to the sipe length in this manner, it is possible to achieve both improvement of the driving stability performance on a dry road surface and improvement of the driving stability performance on a wet road surface. More preferably from-15% to 15%.

In the present invention, it is preferable that the chamfered portion is provided at one location on each of the edges on the step-in side and the kick-out side of the sipe. By disposing the chamfered portion in this manner, uneven wear resistance can be improved.

In the present invention, it is preferable that the maximum width of the chamfered portion is set to 0.8 to 5.0 times the sipe width of the sipe. By setting the maximum width of the chamfered portion appropriately with respect to the sipe width in this manner, it is possible to achieve both improvement of the driving stability performance on a dry road surface and improvement of the driving stability performance on a wet road surface. More preferably 1.2 times to 3.0 times.

In the present invention, it is preferable that the chamfered portion extends in parallel with the sipe. This improves uneven wear resistance, and can achieve both improvement in driving stability on dry road surfaces and improvement in driving stability on wet road surfaces.

Drawings

Fig. 1 is a meridian cross-sectional view showing a pneumatic tire including an embodiment of the present invention.

Fig. 2 is a perspective view showing a part of a tread portion of the pneumatic tire of the present invention.

Fig. 3 is a plan view showing a part of a tread portion of the pneumatic tire of the present invention.

Fig. 4 is a plan view showing a sipe formed in the tread portion of fig. 3 and a chamfered portion thereof.

Fig. 5 is an X-X sectional view of fig. 3.

Fig. 6 is a Y-Y sectional view of fig. 3.

Fig. 7(a) and 7(b) show modified examples of the sipe and the chamfered portion of the pneumatic tire according to the present invention, and fig. 7(a) and 7(b) are plan views of the modified examples.

Fig. 8(a) to 8(e) show other modifications of the sipe and the chamfered portion of the pneumatic tire according to the present invention, and fig. 8(a) to 8(e) are plan views of the modifications.

Detailed Description

Hereinafter, the configuration of the present invention will be described in detail with reference to the drawings. In fig. 1, CL is a tire centerline.

As shown in fig. 1, a pneumatic tire including an embodiment of the present invention includes a tread portion 1 extending in a circumferential direction of the tire and having a ring shape, a pair of

sidewall portions

2,2 disposed on both sides of the tread portion 1, and a pair of

bead portions

3,3 disposed on inner sides of the sidewall portions 2 in a tire radial direction.

A carcass layer 4 is mounted between the pair of

bead portions

3, 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the tire inner side to the outer side around bead cores 5 disposed in the respective bead portions 3. A bead filler 6 made of a rubber composition having a triangular cross section is disposed on the outer periphery of the bead core 5.

On the other hand, a plurality of belt layers 7 are embedded on the outer circumferential side of the carcass layer 4 of the tread portion 1. These belt layers 7 contain a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are configured such that the reinforcing cords cross each other between the layers. In the belt layer 7, the inclination angle of the reinforcing cords with respect to the tire circumferential direction is set in the range of, for example, 10 ° to 40 °. As the reinforcing cords of the belt layer 7, steel cords are preferably used. At least one belt cover layer 8 in which reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction is disposed on the outer circumferential side of the belt layer 7 for the purpose of improving high-speed durability. As the reinforcing cord of the belt cover layer 8, an organic fiber cord of nylon, aramid, or the like is preferably used.

Further, a plurality of main grooves 9 extending in the circumferential direction of the tire are formed in the tread portion 1, and a plurality of rows of ribs 10 are defined in the tread portion 1 by these main grooves 9.

The tire internal structure described above shows a typical example of a pneumatic tire, but is not limited to this.

Fig. 2 is a perspective view showing a part of the tread portion 1, Tc shown in fig. 2 is the tire circumferential direction, and Tw is the tire width direction. As shown in fig. 2, the rib 10 includes a plurality of sipes 11 extending in the tire width direction and blocks 101 defined by the plurality of sipes 11. The plurality of blocks 101 are arranged in parallel in the tire circumferential direction. The sipe 11 is a narrow groove having a groove width of 1.5mm or less.

As shown in fig. 3, the overall shape of the sipe 11 has a curved shape, and is formed in the rib 10 at intervals in the tire circumferential direction. Further, the sipe 11 has an edge 11A on the step-in side with respect to the rotation direction R and an edge 11B on the kick-out side with respect to the rotation direction R. Chamfered portions 12 are formed on the edge 11A on the step-in side and the edge 11B on the kick-out side, respectively.

The chamfered portion 12 includes a chamfered portion 12A on a step-in side with respect to the rotation direction R and a chamfered portion 12B on a kick-out side with respect to the rotation direction R. At positions opposed to these chamfered portions 12, non-chamfered regions 13 having no other chamfered portion are present. That is, a non-chamfered region 13B on the kick-out side with respect to the rotation direction R exists at a position facing the chamfered portion 12A, and a non-chamfered region 13A on the step-in side with respect to the rotation direction R exists at a position facing the chamfered portion 12B. As described above, the chamfered portion 12 and the non-chamfered region 13 where no other chamfered portion exists are disposed so as to be adjacent to each other at the edge 11A on the step-in side and the edge 11B on the kick-out side of the sipe 11.

As shown in FIG. 4, the sipe 11 and the

chamfered portions

12A,12B have a sipe length L and a chamfer length L, respectively, in the tire width direction_A、L_B. The sipe length L and chamfer length L_A、L_BThe length of the sipe 11 or the

chamfered portions

12A,12B in the tire width direction is from one end to the other end. Chamfer length L of

chamfer

12A,12B_A、L_BAre formed to be shorter than the sipe length L of the sipe 11.

Fig. 5 is a cross-sectional view of the tread portion 1 cut perpendicularly to the sipe 11. As shown in fig. 5, when the maximum depth of the sipe 11 is x (mm) and the maximum depth of the chamfered portion 12 is y (mm), the sipe 11 and the chamfered portion 12 are formed such that: the maximum depth x (mm) and the maximum depth y (mm) satisfy the relationship of the following equation (1). The maximum depth x of the sipe 11 is preferably 3mm to 8 mm. The sipe width W of the sipe 11 is substantially constant in a range from the end 121 of the chamfered portion 12 located on the inner side in the tire radial direction to the groove bottom of the sipe 11. For example, in the case where a protrusion is present in the groove wall of the sipe 11, the sipe width W is a value at which the height of this protrusion is not included in the sipe width, or in the case where the sipe width of the sipe 11 is gradually narrowed toward the groove bottom, the sipe width W is a portion at which the narrowing is not included in the sipe width, which is the actually measured width of the sipe 11.

x×0.1≤y≤x×0.3+1.0 (1)

In the pneumatic tire described above, the chamfered portions 12 shorter than the sipe length L of the sipe 11 are provided on each of the edge 11A on the step-in side and the edge 11B on the kick-out side of the sipe 11, and the non-chamfered regions 13 having no other chamfered portion are present at positions of the sipe 11 opposed to each chamfered portion 12, whereby the water drainage effect can be improved by the chamfered portions 12, and the water film can be effectively removed by the edge effect in the non-chamfered regions 13 having no chamfered portion 12. Therefore, the driving stability on a wet road surface can be greatly improved. Further, since the chamfered portion 12 and the non-chamfered portion 13 where no chamfered portion is present are mixed in the rim 11A on the step-in side and the rim 11B on the kick-out side, the above-described effect of improving the moisture performance can be enjoyed to the maximum extent at the time of braking and driving.

In the pneumatic tire, the maximum depth x (mm) and the maximum depth y (mm) need to satisfy the relationship of the above equation (1). By providing the sipe 11 and the chamfered portion 12 so as to satisfy the relationship of the above equation (1), the area to be chamfered can be minimized as compared with a conventional chamfered sipe, and therefore, the driving stability on a dry road surface can be improved. As a result, the improvement of the driving stability performance on a dry road surface and the improvement of the driving stability performance on a wet road surface can be achieved at the same time. Here, when y < x × 0.1, the drainage effect by the chamfered portion 12 becomes insufficient, and conversely, when y > x × 0.3+1.0, the steering stability performance on a dry road surface is lowered by the decrease in rigidity of the rib 10. In particular, it is preferable that y.ltoreq.x0.3 +0.5 is satisfied.

As shown in fig. 2, the sipe 11 is an open sipe passing through the rib 10 in the tire width direction. That is, both end portions of the sipe 11 communicate with the main grooves 9 located on both sides of the rib 10. As described above, since both ends of the sipe 11 are opened to the main groove 9, the balance of the rigidity of the rib 10 can be improved, and as a result, the uneven wear resistance can be improved.

Further, as shown in fig. 4, the sipe 11 is formed to have an inclination angle θ with respect to the tire circumferential direction. The inclination angle θ is an angle formed by a virtual line (a broken line shown in fig. 4) connecting both end portions of the sipe 11 and the side surface of the block 101, and the inclination angle θ includes an acute-angle-side inclination angle and an obtuse-angle-side inclination angle, and fig. 4 shows the acute-angle-side inclination angle θ. The inclination angle θ is directed to the inclination angle of the sipe 11 at the intermediate pitch in the rib 10. At this time, it is preferable that the inclination angle θ of the acute angle side is 40 ° to 80 °, more preferably 50 ° to 70 °. By inclining the sipe 11 with respect to the tire circumferential direction in this manner, the pattern rigidity can be improved, and the steering stability performance on a dry road surface can be further improved. Here, when the inclination angle θ is less than 40 °, uneven wear resistance is deteriorated, and when it exceeds 80 °, pattern rigidity cannot be sufficiently improved.

In the present invention, the side of the sipe 11 having the inclination angle θ on the acute angle side is referred to as the acute angle side, and the side of the sipe 11 having the inclination angle θ on the obtuse angle side is referred to as the obtuse angle side.

Chamfered portions

12A,12B formed at

edges

11A,11B of the sipe 11, respectively, are formed at the acute-angled side of the sipe 11. By chamfering the acute-angled side of the sipe 11 in this manner, uneven wear resistance can be further improved. Alternatively, the

chamfered portions

12A,12B may be formed on the obtuse-angle side of the sipe 11. By forming the

chamfered portions

12A,12B on the obtuse-angle side of the sipe 11 in this manner, the edge effect is enhanced, and the driving stability performance on a wet road surface can be further improved.

In the present invention, the overall shape of the sipe 11 is curved, so that the steering stability on a wet road surface can be improved, and a part of the sipe 11 may have a curved or bent shape in a plan view. By forming the sipe 11 in this manner, the total amount of the

edges

11A,11B of each sipe 11 increases, and the steering stability on a wet road surface can be improved.

As shown in fig. 2 and 3, the end portions of the chamfered

portions

12A,12B near the main groove 9 communicate with the main grooves 9 on both sides of the rib 10, respectively. By forming the

chamfered portions

12A,12B in this manner, the driving stability performance on a wet road surface can be further improved. Alternatively, the ends of the chamfered

portions

12A,12B located near the main groove 9 may not communicate with the main groove 9 but terminate within the rib 10. By forming the

chamfered portions

12A,12B in this manner, the steering stability performance on a dry road surface can be further improved.

As shown in fig. 7(a), the chamfered portion 12A and the chamfered portion 12B are formed such that: in the central portion of the sipe 11, a part of both the

chamfered portions

12A,12B overlaps. Here, the length in the tire width direction of the overlapping portion, which is the portion where the chamfered portion 12A and the chamfered portion 12B overlap, is defined as an overlapping length L1. On the other hand, as shown in fig. 7(B), when the chamfered portion 12A and the chamfered portion 12B are not partially overlapped but separated at a constant interval, the ratio of the overlap length L1 to the sipe length L is represented by a negative value. Preferably, the overlap length L1 of the overlap is-30% to 30%, more preferably-15% to 15% of the sipe length L. By appropriately setting the overlap length L1 of the chamfered

portions

12A,12B with respect to the sipe length L in this manner, it is possible to achieve both improvement of the driving stability performance on a dry road surface and improvement of the driving stability performance on a wet road surface. Here, when the overlap length L1 is greater than 30%, the improvement in driving stability performance on a dry road surface becomes insufficient, and when it is less than-30%, the improvement in driving stability performance on a wet road surface becomes insufficient.

As shown in fig. 3, the chamfered portion 12 is disposed at one position on each of the step-in side edge 11A and the kick-out side edge 11B of the sipe 11. By disposing the chamfered portion 12 in this manner, uneven wear resistance can be improved. Here, when the chamfer portion 12 is formed at two or more positions on each of the step-in side edge 11A and the kick-out side edge 11B of the sipe 11, the number of steps increases, and uneven wear resistance tends to deteriorate.

The maximum value of the width of the chamfered portion 12 measured in the direction orthogonal to the sipe 11 is defined as the width W1. At this time, the maximum width W1 of the chamfered portion 12 is preferably 0.8 to 5.0 times, more preferably 1.2 to 3.0 times the sipe width W of the sipe 11. By appropriately setting the maximum width W1 of the chamfered portion 12 with respect to the sipe width in this manner, it is possible to achieve both improvement of the driving stability performance on a dry road surface and improvement of the driving stability performance on a wet road surface. Here, when the maximum width W1 of the chamfered portion 12 is less than 0.8 times the sipe width W of the sipe 11, improvement of the driving stability performance on a wet road surface becomes insufficient, and when it is more than 5.0 times, improvement of the driving stability performance on a dry road surface becomes insufficient.

Further, the outer edge portion of the chamfered portion 12 in the longitudinal direction is formed parallel to the extending direction of the sipe 11. As described above, the chamfered portion 12 extends in parallel with the sipe 11, so that the uneven wear resistance can be improved, and the improvement of the driving stability performance on a dry road surface and the improvement of the driving stability performance on a wet road surface can be both achieved.

As shown in fig. 6, the sipe 11 has a raised portion 14 in a part of its longitudinal direction. As the raised portions 14, there are a raised portion 14A located at the center of the sipe 11 and raised portions 14B located at both ends of the sipe 11. By providing the raised portion 14 in the sipe 11 in this manner, it is possible to achieve both improvement in driving stability performance on a dry road surface and improvement in driving stability performance on a wet road surface. The raised portions 14 of the sipe 11 may also be formed at the ends and/or beyond the ends of the sipe 11.

In the raised part 14A formed in the sipe 11 except the end part, the distance from the groove bottom of the sipe 11 to the upper surface of the raised part 14A is set to be longerIs set as height H_14A. Preferably, the height H_14APreferably 0.2 to 0.5 times, more preferably 0.3 to 0.4 times the maximum depth x of the sipe 11. In this way, the height H of the raised portion 14A disposed at the end portion other than the sipe 11 is increased_14ASetting the height to an appropriate level can increase the rigidity of the block 101 and maintain the drainage effect, and therefore can improve the steering stability on a wet road surface. Herein, when the height H is_14AWhen the depth x is less than 0.2 times the maximum depth x of the sipe 11, the rigidity of the block 101 cannot be sufficiently improved, and when the depth x is more than 0.5 times, the driving stability on a wet road cannot be sufficiently improved.

In the raised portions 14B formed at both ends of the sipe 11, the maximum value of the height from the groove bottom of the sipe 11 to the upper surface of the raised portion 14B is defined as the height H_14B. Preferably, this height H_14BPreferably 0.6 to 0.9 times, more preferably 0.7 to 0.8 times the maximum depth x of the sipe 11. In this way, the height H of the raised portion 14B formed at the end of the sipe 11 is increased_14BSetting the height to an appropriate level can improve the rigidity of the block 101, and can improve the steering stability on a dry road surface. Herein, when the height H is_14BWhen the depth x is less than 0.6 times the maximum depth x of the sipe 11, the rigidity of the block 101 cannot be sufficiently improved, and when the depth x is more than 0.9 times, the driving stability on a wet road cannot be sufficiently improved.

In the raised

portions

14A,14B of the sipe 11, the length in the tire width direction is set to the raised length L_14A、L_14B. Preferably, these elevated lengths L_14A、L_14BThe sipe length L is preferably 0.3 to 0.7 times, more preferably 0.4 to 0.6 times. By appropriately setting the elevation lengths L of the

elevated portions

14A,14B in this manner_14A、L_14BThe driving stability performance on dry road surfaces and the driving stability performance on wet road surfaces can be improved at the same time.

As the

chamfered portions

12A,12B of the sipe 11, the following may be exemplified in addition to those shown in fig. 2 to 4, 7(a), and 7 (B): as shown in fig. 8(a), a case where chamfering is performed on the obtuse-angle side of the sipe 11; as shown in fig. 8(b), a case where a part of the sipe 11 is flexed; and as shown in fig. 8(c), the respective ends of the chamfered

portions

12A,12B located in the vicinity of the main groove 9 do not open in the main groove 9 but terminate in the rib 10. Further, the following can be exemplified: as shown in fig. 8(d), the case where the sipe 11 and the

chamfered portions

12A,12B are formed parallel to the tire width direction; and as shown in fig. 8(e), the boundary line between the chamfered portion 12A and the chamfered portion 12B in the tire width direction is greatly offset from the center of the sipe 11.

Examples of the invention

Tires of conventional examples 1 and 2, comparative examples 1 and 2, and examples 1 to 14 were produced as follows: the pneumatic tire has a tire size of 245/40R19, has a plurality of main grooves extending in the circumferential direction of the tire in the tread portion, and has sipes extending in the tire width direction in ribs defined by the main grooves, wherein the following are set as shown in tables 1 and 2: chamfer configuration (either two-sided or one-sided), sipe length L, and chamfer length L_AAnd L_BThe length of (2), the presence or absence of a chamfer at a position opposed to the chamfer, the maximum depth x (mm) of the sipe, the maximum depth y (mm) of the chamfer, the structure (communication or non-communication) of the sipe, the angle of inclination of the sipe with respect to the acute angle side in the tire circumferential direction, the chamfer position (obtuse angle side or acute angle side) of the sipe, the shape (straight line or curve) of the entire sipe, the presence or absence of an opening of the chamfer to the main groove, the ratio of the overlap length L1 of the chamfer to the sipe length L, the number (one or two) of chamfer positions, the maximum width W1 of the chamfer with respect to the sipe width W (W1/W), the shape (parallel or non-parallel), the presence or absence of a raised portion of the sipe, and the height of a raised portion other than the end portion of the sipe with respect to the maximum depth x (H1/W) of the sipe_14A/x)。

Sensory evaluation on the steering stability performance on a dry road surface and the steering stability performance on a wet road surface and visual evaluation on the uneven wear resistance performance by a test driver were performed on these test tires, and the results are shown in tables 1 and 2.

In tables 1 and 2, regarding the sipe structure, a case where both ends of the sipe communicate with the main grooves located on both sides of the rib is referred to as "communicating", and a case where both ends of the sipe do not communicate with the main grooves and terminate in the rib is referred to as "non-communicating". In the tires of conventional example 1, comparative examples 1 and 2, and examples 1 to 14, the sipe width was constant in the range from the end portion of the chamfered portion located on the inner side in the tire radial direction to the groove bottom of the sipe.

In sensory evaluation on the steering stability performance on a dry road surface and the steering stability performance on a wet road surface, each test tire was assembled to a wheel having a rim size of 19 × 8.5J and mounted to a vehicle under a condition of an air pressure of 260 kPa. The evaluation results are expressed as an index with the conventional example 1 set to 100. The larger the index value, the more excellent the driving stability performance on a dry road surface and the driving stability performance on a wet road surface.

In the visual evaluation of the uneven wear resistance performance, each test tire was assembled to a wheel having a rim size of 19 × 8.5J and attached to a vehicle, and after running 4000km under a condition of an air pressure of 260kPa, the appearance of the tire was visually evaluated. The evaluation results are expressed as an index with the conventional example 1 set to 100. The larger the index value, the more excellent the uneven wear resistance is.

From these tables 1 and 2, it is judged that the tires of examples 1 to 14 are improved in uneven wear resistance and improved in both driving stability on dry road surfaces and driving stability on wet road surfaces by designing the shape formed in the chamfered portion of the sipe.

On the other hand, in comparative example 1, the maximum depth y of the chamfered portion is set very shallow, and therefore the effect of improving the driving stability performance on a wet road surface cannot be obtained. In comparative example 2, the maximum depth y of the chamfered portion was set very deep, and therefore the effect of improving the steering stability performance on a dry road surface was not obtained.

Description of the symbols

1 tread part

2 side wall part

3 bead portion

9 Main groove

10 Ribs

101 pattern block

11 sipe

11A edge of the stepping side

11B edge of kick-out side

12 chamfered part

12A chamfer part on the step-in side

Chamfer part on 12B kicking side

13 non-chamfered region

13A non-chamfered region on the step-in side

13B kick-out side non-chamfered region

14 raised part

Elevated portion other than end portion of 14A

Elevated portion of 14B end

Claims

1. A pneumatic tire having a plurality of main grooves extending in a tire circumferential direction in a tread portion and sipes extending in a tire width direction in ribs defined by the main grooves,

the sipe has a step-in side edge and a kick-out side edge, chamfered portions shorter than the sipe length of the sipe are formed at the step-in side edge and the kick-out side edge, non-chamfered regions having no other chamfered portion are present at positions of the sipe facing the respective chamfered portions, the maximum depth x (mm) of the sipe and the maximum depth y (mm) of the chamfered portion satisfy the relationship of the following equation (1), and the sipe width of the sipe is constant in a range from an end portion of the chamfered portion located on the inner side in the tire radial direction to the groove bottom of the sipe,

an overlap length of the chamfer formed on the edge of the tread side of the sipe and the chamfer formed on the edge of the kick-out side of the sipe is-30% to 30% of the sipe length, the overlap length being a length measured in the tire width direction, and the overlap length is represented by a negative value in a case where the chamfer formed on the edge of the tread side of the sipe and the chamfer formed on the edge of the kick-out side of the sipe are not overlapped but separated by a fixed interval,

x×0.1≤y≤x×0.3+1.0 (1)，

both end portions of the sipe are opened in the main groove, and raised portions are disposed at both end portions and a central portion of the sipe.

2. A pneumatic tire according to claim 1,

the height of the raised portion disposed outside the end portion of the sipe is 0.2 to 0.5 times the maximum depth x of the sipe.

3. A pneumatic tire according to claim 1 or 2,

the height of the raised portion disposed at the end of the sipe is 0.6 to 0.9 times the maximum depth x of the sipe.

4. A pneumatic tire according to claim 1 or 2,

the sipe is inclined with respect to the tire circumferential direction.

5. A pneumatic tire according to claim 4,

the inclination angle of the sipe with respect to the acute angle side in the tire circumferential direction is 40 ° to 80 °.

6. A pneumatic tire according to claim 4,

the chamfer portion is disposed on an acute angle side of the sipe.

7. A pneumatic tire according to claim 4,

the chamfer portion is disposed on an obtuse angle side of the sipe.

8. A pneumatic tire according to claim 1 or 2,

at least a portion of the sipe is curved or flexed in a top view.

9. A pneumatic tire according to claim 1 or 2,

the chamfered portion opens at the main groove.

10. A pneumatic tire according to claim 1 or 2,

the chamfered portion terminates within the rib.

11. A pneumatic tire according to claim 1 or 2,

the chamfered portion is provided at one location on each of the edges on the step-in side and the kick-out side of the sipe.

12. A pneumatic tire according to claim 1 or 2,

the maximum width of the chamfered portion is set to be 0.8 to 5.0 times the sipe width of the sipe.

13. A pneumatic tire according to claim 1 or 2,

the chamfered portion extends in parallel with the sipe.